The words ode, owed sound the same but have different meanings and spellings. Why do ode, owed sound the same even though they are completely different words?
The answer is simple: ode, owed are homophones of the English language.
A lyric poem of some length, usually of a serious or meditative nature and having an elevated style and formal stanzaic structure.
A choric song of classical Greece, often accompanied by a dance and performed at a public festival or as part of a drama.
A classical Greek poem modeled on the choric ode and usually having a three-part structure consisting of a strophe, an antistrophe, and an epode.
Simple past tense and past participle of owe.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").